1. Field of the Invention
The present invention relates to an illumination apparatus including a plurality of solid-state light sources each configured to emit a light beam having a different directivity, and an optical unit configured to reduce the dispersion angle of a light beam entering thereto, and also relates to a projection display apparatus.
2. Description of the Related Art
Conventionally, a projection display apparatus has been known, which includes a plurality of solid-state light sources each emitting a light beam of a different color, such as red, green or blue (RGB), and projects an image by use of the light beams of the respective colors emitted from the solid-state light sources (Japanese Patent Publication No. 2000-112031).
FIG. 1 shows an example of the aforementioned projection display apparatus. As shown in FIG. 1, the projection display apparatus includes: a multi-chip type light source 10 provided with a plurality of solid-state light sources; a tapered rod integrator 21 configured to lead, to a display panel 30, light beams of the respective colors emitted from the plurality of solid-state light sources; the display panel 30 configured to modulate the light beams of the respective colors entering thereto, and then to emit the modulated light beams as image light; and a projection lens unit 110 configured to project the image light onto a screen or the like.
Normally, a narrow space is provided between the light source 10 and the tapered rod integrator 21 for the purpose of avoiding the transmission of vibration, heat or the like between the two components. However, in order to avoid loss of colored light beams emitted from the light source 10, the light source 10 is preferably arranged as close to the tapered rod integrator 21 as possible in a projection display apparatus of the aforementioned configuration, in general. For this reason, the light source 10 and the tapered rod integrator 21 are arranged as close to each other as possible with a narrow space (approximately 1 mm).
Incidentally, the smaller the dispersion angle of a colored light beam emitted from a solid-state light source is, the higher the light use efficiency of the colored light beam is. Accordingly when a light emitting diode (LED) is utilized as a solid-state light source, an improvement in the directivity of a colored light beam from the solid-state light source is sought by use of a molded lens or photonic crystals.
In a case where a red LED emitting a red light beam, a green LED emitting a green light beam and a blue LED emitting a blue light beam are used as a plurality of solid-state light sources, however, it is difficult to equalize the directivities of the respective light beams emitted from the LEDs.
Specifically, AlInGaP is used as the material of the red LED emitting a red light beam while InGaN is used as the material of the green LED and blue LED respectively emitting a green light beam and blue light beam. Accordingly, the distribution of the dispersion angle of the red LED results in as shown in FIG. 2A, while the distribution of the dispersion angle of each of the green and blue LEDs results in as shown in FIG. 2B, for example. In particular, the difference between the light intensities of the red LED, and the green and blue LEDs in the dispersion angle range of 30° to 60°, and in the range of −30° and −60°, is large.
As described above, in a projection display apparatus that employs color LEDs each having a different directivity, a difference in luminance distributions (unevenness of the brightness on the illuminated surface), dispersion angle distributions (the distribution states shown in FIGS. 2A and 2B), surface dispersion angle distributions (dispersion angle distributions in the respective portions on the illuminated surface) or the like between the respective colored light beams occurs in a case where the colored light beams are led to the display panel 30 by use of optical systems having the same mechanism. For this reason, a color shading occurs in a projected image on a screen, which significantly deteriorates the quality of the image.